Nowadays, an actuator that is controlled by a controller to move an object, such as a workpiece or a product, in a predetermined direction is employed in various apparatuses such as semiconductor manufacturing apparatuses, various kinds of machine tools, and a conveyer. An apparatus including such an actuator (hereinafter, “vibration excitation actuator”) vibrates inevitably because a reaction force induced by the operation of the vibration excitation actuator becomes a vibration exciting force. Particularly, in an apparatus including a vibration excitation actuator that obtains thrust by employing a combination of a rotary type motor and a ball screw, a vibration excitation actuator that obtains thrust with a linear motor, or the like, a comparatively large vibration exciting force is produced at the time of acceleration or deceleration for moving an object.
When a large vibration exciting force acts on a machine tool when machining an object, processing accuracy degrades because a vibration excitation actuator and a workpiece are vibrated due to the vibration of the machine tool. In this case, the machine tool can be the machine tool mentioned above that machines a workpiece while moving a tool by means of the vibration excitation actuator or the machine tool mentioned above that machines a workpiece while moving the workpiece by means of the vibration excitation actuator. To machine a workpiece with high form accuracy and high positional accuracy, it is preferable to suppress the vibration of the apparatus (machine tool) as much as possible, which is induced by the operation of a vibration excitation actuator. Moreover, in a conveyer that conveys a conveying target object, such as a workpiece or a product, to a predetermined point by moving the conveying target object by means of the vibration excitation actuator, it is preferable that a vibration exciting force induced by the operation of the vibration excitation actuator be suppressed as much as possible so that the conveying target does not hit against the conveyer or another conveying target object or falling down.
An active mass damper described in, for example, Patent Document 1 has been known as a device that employs a technique for suppressing a vibration acting on an apparatus with the operation of a vibration excitation actuator. The active mass damper includes a support device that supports a weight in a horizontal direction, a weight driving device that drives the weight, and a controller that controls the weight driving device, and is arranged in a machining apparatus so that the direction of movement of the weight is parallel to the direction of movement of a first moving unit in the machining apparatus and suppresses the vibration. At this time, the controller performs a feed-forward control on the weight driving device based on a torque command value provided to a driving unit that drives the first moving unit and a torque command value provided to a driving unit that drives another moving unit, and also performs a feedback control on the weight driving device based on the displacement of the weight.
Patent Document 1: Japanese Patent Application Laid-open No. 2005-212008